Using a side-communication channel for exchanging radar information to improve multi-radar coexistence

ABSTRACT

Methods, systems, and devices for wireless communications are described. In some systems, radio signals may reach a receiving antenna at a user equipment by two or more paths, which can cause interference (e.g., destructive multipath interference, constructive multipath interference, etc.). To reduce the interference, the user equipment may perform interference suppression, shaping, or both based on choosing radar waveform patterns that are varied across chirps. In one aspect, the user equipment (e.g., a vehicle) may identify waveform patterns selected by nearby vehicles based on side channel or centralized signaling and may suppress or shape interference by selecting waveform parameters based on this information. In one aspect, the pattern of waveform parameters is chosen from a codebook of patterns. The selected pattern can be broadcasted to the other vehicles using a side-communication channel.

CROSS REFERENCES

The present Application for Patent claims the benefit of U.S.Provisional Patent Application No. 62/648,255 by Gulati et al., entitled“Using A Side-Communication Channel For Exchanging Radar Information ToImprove Multi-Radar Coexistence,” filed Mar. 26, 2018, and to U.S.Provisional Patent Application No. 62/648,774 by Gulati et al., entitled“Using A Side-Communication Channel For Exchanging Radar Information ToImprove Multi-Radar Coexistence,” filed Mar. 27, 2018, each of which areassigned to the assignee hereof, and expressly incorporated by referencein their entirety herein.

BACKGROUND

The following relates generally to radar target detection, wirelesscommunication, and more specifically to utilizing a wirelesscommunications system to improve the performance of a radar system in amulti-radar coexistence scenario.

Radar systems are used for target detection by transmitting radiofrequency waveforms and observing the reflected received waveform fromthe target to estimate the properties of the target, such as a distance,speed, and angular location of the target. Radar systems are widely usedfor detection of aircrafts, ships, vehicles, weather formations,terrains, etc. Examples of the transmitted radio frequency waveformsused in radar systems may include frequency modulated continuous waves(FMCWs), phase modulated continuous waves (PMCWs), etc.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems. A wireless multiple-accesscommunications system may include a number of base stations, eachsimultaneously supporting communication for multiple communicationdevices, which may include user equipments (UEs).

Radar may be used in automobiles as sensor input to enable advanceddriver assistance systems (ADAS) and automated driving. Radartransmissions from nearby vehicles, however, may generate significantinterference for the radar systems and may degrade the target detectionperformance.

SUMMARY

The present disclosure relates to methods, systems, devices, andapparatuses that support using a side-communication channel forexchanging radar information. The methods, systems, devices, andapparatuses may improve multi-radar coexistence in a wirelesscommunications system.

A method for suppressing interference implemented by a UE with a radarin a communication system is described. The method may include selectingwaveform parameters for transmission of a radar waveform, where theradar waveform includes a set of chirps and the selecting includesvarying the waveform parameters for at least one chirp of the set ofchirps, transmitting an indication of one or more of the selectedwaveform parameters over the communication system, and transmitting theradar waveform according to the selected waveform parameters.

An apparatus for suppressing interference implemented by a UE with aradar in a communication system is described. The apparatus may includea processor, memory in electronic communication with the processor, andinstructions stored in the memory. The instructions may be executable bythe processor to cause the apparatus to select waveform parameters fortransmission of a radar waveform, where the radar waveform includes aset of chirps and the selecting includes varying the waveform parametersfor at least one chirp of the set of chirps, transmit an indication ofone or more of the selected waveform parameters over the communicationsystem, and transmit the radar waveform according to the selectedwaveform parameters.

Another apparatus for suppressing interference implemented by a UE witha radar in a communication system is described. The apparatus mayinclude means for selecting waveform parameters for transmission of aradar waveform, where the radar waveform includes a set of chirps andthe selecting includes varying the waveform parameters for at least onechirp of the set of chirps, transmitting an indication of one or more ofthe selected waveform parameters over the communication system, andtransmitting the radar waveform according to the selected waveformparameters.

A non-transitory computer-readable medium storing code for suppressinginterference implemented by a UE with a radar in a communication systemis described. The code may include instructions executable by aprocessor to select waveform parameters for transmission of a radarwaveform, where the radar waveform includes a set of chirps and theselecting includes varying the waveform parameters for at least onechirp of the set of chirps, transmit an indication of one or more of theselected waveform parameters over the communication system, and transmitthe radar waveform according to the selected waveform parameters.

In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the selecting the waveformparameters may include operations, features, means, or instructions forselecting a codeword from a codebook including a set of codewords, wherethe codeword indicates the selected waveform parameters.

In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the selecting the waveformparameters may include operations, features, means, or instructions foridentifying a set of codewords for additional UEs within a thresholddistance and varying the waveform parameters for the at least one chirpwith uniform distribution within a range such that a distance may bemaximized between the selected codeword and the identified set ofcodewords.

In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the transmitting theindication of the one or more of the selected waveform parameters mayinclude operations, features, means, or instructions for broadcastingthe indication of the one or more of the selected waveform parameters onone or more side-communication channels between the UE and one or moreadditional UEs.

In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the transmitting theindication of the one or more of the selected waveform parameters mayinclude operations, features, means, or instructions for transmittingthe indication of the one or more of the selected waveform parameters onan uplink (UL) channel between the UE and a network entity.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving, from anetwork entity, information of a set of codewords being used inproximity to the UE.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for broadcasting a beacon,a coded discovery message, or a combination thereof on one or moreside-communication channels between the UE and one or more additionalUEs to indicate a location of the UE.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving informationof a set of codewords used by additional UEs on one or moreside-communication channels between the UE and one or more of theadditional UEs, where the waveform parameters may be varied based on theinformation of the set of codewords used by the additional UEs.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving a set ofbeacons, a set of coded discovery messages, or a combination thereof forthe additional UEs on the one or more side-communication channelsbetween the UE and the one or more of the additional UEs to indicatelocations of the additional UEs and determining a set of proximityvalues for the additional UEs with respect to the UE, where the waveformparameters may be varied based on the set of proximity values for theadditional UEs.

In some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the selected waveformparameters include a frequency range, a chirp duration, a frequencyoffset, or a combination thereof.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying, for theradar waveform, a range of interest for interference sources and settinga frequency offset for the radar waveform such that an interference peakof at least one interference source appears beyond the range ofinterest.

Some aspects of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for phase-coding one ormore chirps of the radar waveform to avoid coherent addition of chirpswith other radar waveforms in the communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example wireless network in accordance withaspects of the present disclosure.

FIG. 2 illustrates an example logical architecture of a distributedradio access network (RAN) in accordance with aspects of the presentdisclosure.

FIG. 3 illustrates an example physical architecture of a distributed RANin accordance with aspects of the present disclosure.

FIG. 4 illustrates example components of a base station and a userequipment (UE) in a wireless communications system in accordance withaspects of the present disclosure.

FIG. 5A illustrates an example of a downlink (DL)-centric subframe inaccordance with aspects of the present disclosure.

FIG. 5B illustrates an example of an uplink (UL)-centric subframe inaccordance with aspects of the present disclosure.

FIG. 6A illustrates an example wireless communications system inaccordance with aspects of the present disclosure.

FIG. 6B illustrates an example graph showing received power of directand reflected signals over distance in accordance with aspects of thepresent disclosure.

FIGS. 7A and 7B illustrate frequency-time plots of a frequency modulatedcontinuous wave (FMCW) with different parameters in accordance withaspects of the present disclosure. FIG. 7A illustrates unvaried waveformparameters, while FIG. 7B illustrates variations in the slope β and/orthe frequency offset f parameters.

FIG. 8 illustrates an FMCW system with received and transmitted rampwaveforms with sawtooth chirp modulation in accordance with aspects ofthe present disclosure.

FIG. 9 is a flowchart illustrating a method for enabling the coexistenceof multiple radar sources by a UE, where the UE may suppress radarinterference in a communication system in accordance with aspects of thepresent disclosure.

FIG. 10 is a flowchart illustrating a method for enabling thecoexistence of multiple radar sources by UEs including suppressing radarinterference in a communication system in accordance with aspects of thepresent disclosure.

FIG. 11 illustrates certain components that may be included within abase station.

FIG. 12 illustrates certain components that may be included within awireless communication device.

DETAILED DESCRIPTION

In some wireless communications systems, such as 5th Generation (5G) NewRadio (NR) systems, transmission waveforms may include cyclic prefixorthogonal frequency division multiplexing (CP-OFDM) and discreteFourier transform-spread (DFT-S) OFDM. 5G allows for switching betweenboth CP-OFDM and DFT-S-OFDM on the uplink (UL) to get the multiple inputmultiple output (MIMO) spatial multiplexing benefit of CP-OFDM and thelink budget benefit of DFT-S-OFDM. With Long Term Evolution (LTE),orthogonal frequency division multiple access (OFDMA) communicationsignals may be used for downlink (DL) communications, whilesingle-carrier frequency division multiple access (SC-FDMA)communication signals may be used for LTE UL communications. TheDFT-s-OFDMA scheme spreads a set of data symbols (i.e., a data symbolsequence) over a frequency domain which is different from the OFDMAscheme. Also, in comparison to the OFDMA scheme, the DFT-s-OFDMA schemecan greatly reduce the peak to average power ratio (PAPR) of atransmission signal. The DFT-s-OFDMA scheme may also be referred to asan SC-FDMA scheme.

Scalable OFDM multi-tone numerology is another feature of 5G. Priorversions of LTE supported a mostly fixed OFDM numerology of fifteen (15)kilohertz (kHz) spacing between OFDM tones (often called subcarriers)and carrier bandwidths up to twenty (20) megahertz (MHz). Scalable OFDMnumerology has been introduced in 5G to support diverse spectrumbands/types and deployment models. For example, 5G NR is able to operatein millimeter wave (mmW) bands that have wider channel widths (e.g.,hundreds of MHz) than bands in use in LTE. Also, the OFDM subcarrierspacing may scale with the channel width, so the fast Fourier transform(FFT) size may also scale such that the processing complexity does notincrease unnecessarily for wider bandwidths. In the present application,numerology may refer to the different values that different features(e.g., subcarrier spacing, cyclic prefix (CP), symbol length, FFT size,transmission time interval (TTI), etc.) of a communication system cantake.

Also in 5G NR, cellular technologies have been expanded into theunlicensed spectrum (e.g., both stand-alone and licensed-assisted access(LAA)). In addition, the unlicensed spectrum may occupy frequencies upto sixty (60) gigahertz (GHz), also known as mmW. The use of unlicensedbands provides added capacity for communications in the system.

A first member of this technology family is referred to as LTEUnlicensed (LTE-U). By aggregating LTE in unlicensed spectrum with an‘anchor’ channel in licensed spectrum, faster downloads are enabled forcustomers. Also, LTE-U may share the unlicensed spectrum fairly withWi-Fi. This is an advantage because in the five (5) GHz unlicensed bandwhere Wi-Fi devices are in wide use, it is desirable for LTE-U tocoexist with Wi-Fi. However, an LTE-U network may cause radio frequency(RF) interference to an existing co-channel Wi-Fi device. Choosing apreferred operating channel and minimizing the interference caused tonearby Wi-Fi networks may be a goal for LTE-U devices. However, an LTE-Usingle carrier (SC) device may operate on the same channel as Wi-Fi ifall available channels are occupied by Wi-Fi devices. To coordinatespectrum access between LTE-U and Wi-Fi, the energy across the intendedtransmission band may first be detected. This energy detection (ED)mechanism informs the device of ongoing transmissions by other nodes.Based on this ED information, a device decides if it should transmit onthe intended transmission band. Wi-Fi devices may not back off for LTE-Utransmissions unless the interference level caused by the LTE-Utransmissions is above an ED threshold (e.g., negative sixty-two (−62)decibel-milliwatts (dBm) over 20 MHz). Thus, without proper coexistencemechanisms in place, LTE-U transmissions could cause considerableinterference on a Wi-Fi network relative to Wi-Fi transmissions.

LAA is another member of the unlicensed technology family. Like LTE-U,it may also use an anchor channel in licensed spectrum. However, it alsoadds “listen before talk” (LBT) operations to the LTE functionality.

A gating interval may be used to gain access to a channel of a sharedspectrum. The gating interval may determine the application of acontention-based protocol such as an LBT protocol. The gating intervalmay indicate when a clear channel assessment (CCA) is performed. Whethera channel of the shared unlicensed spectrum is available or in use isdetermined by the CCA. If the channel is “clear” for use, i.e.,available, the gating interval may allow the transmitting apparatus touse the channel. Access to the channel is typically granted for apredefined transmission interval. Thus, with unlicensed spectrum, a“listen before talk” procedure is performed before transmitting amessage. If the channel is not cleared for use, then a device will nottransmit on the channel.

Another member of this family of unlicensed technologies is LTE-wirelesslocal area network (WLAN) Aggregation (LWA), which may utilize both LTEand Wi-Fi. Accounting for both channel conditions, LWA can split asingle data flow into two data flows which allows both the LTE and theWi-Fi channel to be used for an application. Instead of competing withWi-Fi, the LTE signal may use the WLAN connections seamlessly toincrease capacity.

The final member of this family of unlicensed technologies is MulteFire.MulteFire opens up new opportunities by operating Fourth Generation (4G)LTE technology solely in unlicensed spectrum such as the global 5 GHz.Unlike LTE-U and LAA, MulteFire may support entities without any accessto the licensed spectrum. Thus, it operates in unlicensed spectrum on astandalone basis (e.g., without any anchor channel in the licensedspectrum). Thus, MulteFire differs from LTE-U, LAA, and LWA becauseLTE-U, LAA, and LWA aggregate unlicensed spectrum with an anchor inlicensed spectrum. Without relying on licensed spectrum as the anchoringservice, MulteFire allows for Wi-Fi-like deployments. A MulteFirenetwork may include access points (APs) and/or base stationscommunicating in an unlicensed radio frequency spectrum band (e.g.,without a licensed anchor carrier).

Discovery reference signal (DRS) measurement timing configuration (DMTC)is a technique that allows MulteFire to transmit with minimal or reducedinterference to other unlicensed technologies, including Wi-Fi.Additionally, the periodicity of discovery signals in MulteFire may bevery sparse. This allows Multefire to access channels occasionally,transmit discovery and control signals, and then vacate the channels.Since the unlicensed spectrum is shared with other radios of similar ordissimilar wireless technologies, a so-called LBT method may be appliedfor channel sensing. LBT may include sensing the medium for apre-defined minimum amount of time and backing off if the channel isbusy. Therefore, the initial random access (RA) procedure for standaloneLTE-U may involve a minimal number of transmissions with low latency,such that the number of LBT operations may be minimized or reduced andthe RA procedure may be completed quickly.

Leveraging a DMTC window, MulteFire algorithms may search and decodereference signals in unlicensed bands from neighboring base stations inorder to find which base station to select to serve the user. As thecaller moves past one base station, their user equipment (UE) may send ameasurement report to the base station, triggering a handover procedureand transferring the caller (and all of their content and information)to the next base station.

Since LTE traditionally operates in licensed spectrum and Wi-Fi operatesin unlicensed bands, coexistence with Wi-Fi or other unlicensedtechnology was not considered when LTE was designed. In moving to theunlicensed world, the LTE waveform was modified and algorithms wereadded in order to perform LBT. This may support the ability to share achannel with unlicensed incumbents, including Wi-Fi, by not immediatelyacquiring the channel and transmitting. The present example supports LBTand the detection and transmission of Wi-Fi Channel Usage Beacon Signals(WCUBSs) for ensuring coexistence with Wi-Fi neighbors.

MulteFire was designed to “hear” a neighboring Wi-Fi base station'stransmission. MulteFire may listen first and autonomously make thedecision to transmit when there is no other neighboring Wi-Fitransmitting on the same channel (e.g., within a threshold range). Thistechnique may ensure co-existence between MulteFire and Wi-Fitransmissions.

The Third Generation Partnership Project (3GPP) and the EuropeanTelecommunications Standards Institute (ETSI) mandate an LBT detectionthreshold (e.g., a negative seventy-two (−72) dBm LBT detectionthreshold). This threshold may further help wireless devices avoidtransmitting messages that interfere with Wi-Fi. MulteFire's LBT designmay be similar or identical to the standards defined in 3GPP forLAA/enhanced LAA (eLAA) and may comply with ETSI rules.

An expanded functionality for 5G involves the use of 5G NR spectrumsharing (NR-SS). 5G NR-SS may enable enhancement, expansion, and/orupgrade of the spectrum sharing technologies introduced in LTE. Theseinclude LTE Wi-Fi Aggregation (LWA), LAA, eLAA, Citizen's BroadbandRadio service (CBRS)/License Shared Access (LSA), or any combination ofthese technologies.

Aspects of the disclosure are initially described in the context of awireless communication system. Aspects of the disclosure are thenillustrated by and described with reference to apparatus diagrams,system diagrams, and flowcharts that relate to using aside-communication channel for exchanging radar information to improvemulti-radar coexistence.

FIG. 1 illustrates an example wireless network 100 (e.g., an NR network,a 5G network, or any other type of wireless communications network orsystem) in accordance with aspects of the present disclosure.

As illustrated in FIG. 1 , the wireless network 100 may include a numberof base stations 110 and other network entities. A base station 110 maybe a station that communicates with UEs 120. Each base station 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” may refer to a coverage area of a Node B and/or aNode B subsystem serving this coverage area, depending on the context inwhich the term is used. In NR systems, the term “cell” and evolved NodeB (eNB), Node B, 5G NB, AP, NR base station, 5G Radio NodeB (gNB), ortransmission/reception point (TRP) may be interchangeable. In someaspects, a cell may not necessarily be stationary, and the geographicarea of the cell may move according to the location of a mobile basestation 120. In some aspects, the base stations 110 may beinterconnected to one another and/or to one or more other base stations110 or network nodes (not shown) in the wireless network 100 throughvarious types of backhaul interfaces such as a direct physicalconnection, a virtual network, or the like using any suitable transportnetwork.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, etc. Each frequency may support a single RAT in a givengeographic area in order to avoid interference between wireless networksof different RATs. In some cases, NR or 5G RAT networks may be deployed.

A base station 110 may provide communication coverage for a macro cell,a pico cell, a femto cell, and/or other types of cell. A macro cell maycover a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs 120 with servicesubscription. A pico cell may cover a relatively small geographic areaand may allow unrestricted access by UEs 120 with service subscription.A femto cell may cover a relatively small geographic area (e.g., a home)and may allow restricted access by UEs 120 having association with thefemto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for usersin the home, etc.). A base station 110 for a macro cell may be referredto as a macro base station 110. A base station for a pico cell may bereferred to as a pico base station. A base station for a femto cell maybe referred to as a femto base station or a home base station. In theexample shown in FIG. 1 , the base stations 110 a, 110 b, and 110 c maybe macro base stations for the macro cells 102 a, 102 b, and 102 c,respectively. The base station 110 x may be a pico base station for apico cell 102 x. The base stations 110 y and 110 z may be femto basestations for the femto cells 102 y and 102 z, respectively. A basestation may support one or multiple (e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a base station 110 or a UE120) and sends a transmission of the data and/or other information to adownstream station (e.g., a UE 120 or a base station 110). A relaystation may also be a UE 120 that relays transmissions for other UEs120. In the example shown in FIG. 1 , a relay station 110 r maycommunicate with the base station 110 a and a UE 120 r in order tofacilitate communication between the base station 110 a and the UE 120r. A relay station may also be referred to as a relay base station, arelay, etc.

The wireless network 100 may be a heterogeneous network that includesbase stations 110 of different types, e.g., macro base stations, picobase stations, femto base stations, relays, etc. These different typesof base stations may have different transmit power levels, differentcoverage areas, and may have differing impacts on interference in thewireless network 100. For example, a macro base station may have a hightransmit power level (e.g., 20 Watts) whereas a pico base station, or afemto base station, or a relay may have a lower transmit power level(e.g., one (1) Watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the base stations 110 may havesimilar frame timing, and transmissions from different base stations 110may be approximately aligned in time. For asynchronous operation, thebase stations 110 may have different frame timing, and transmissionsfrom different base stations 110 may not be aligned in time. Thetechniques described herein may be used for both synchronous andasynchronous operation.

A network controller 130 may be coupled to a set of base stations 110and provide coordination and control for these base stations 110. Thenetwork controller 130 may communicate with the base stations 110 via abackhaul. The base stations 110 may also communicate with one another,e.g., directly or indirectly via wireless or wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE 120may also be referred to as a mobile station, a terminal, an accessterminal, a subscriber unit, a station, a customer premises equipment(CPE), a cellular phone, a smart phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or medical equipment, a healthcare device, abiometric sensor/device, a wearable device such as a smart watch, smartclothing, smart glasses, virtual reality goggles, a smart wrist band,smart jewelry (e.g., a smart ring, a smart bracelet, etc.), anentertainment device (e.g., a music device, a video device, a satelliteradio, etc.), a vehicular component or sensor, a smart meter/sensor, arobot, a drone, industrial manufacturing equipment, a positioning device(e.g., global positioning system (GPS), Beidou, terrestrial, etc.), orany other suitable device that is configured to communicate via awireless or wired medium. Some UEs 120 may be considered machine-typecommunication (MTC) devices or evolved MTC (eMTC) devices, which mayinclude remote devices that may communicate with a base station 110,another remote device, or some other entity. MTC may refer tocommunication involving at least one remote device on at least one endof the communication and may include forms of data communication whichinvolve one or more entities that do not necessarily need humaninteraction. MTC UEs may include UEs 120 that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMNs), for example. MTC and enhanced MTC (eMTC)UEs include, for example, robots, drones, remote devices, sensors,meters, monitors, cameras, location tags, etc., that may communicatewith a base station 110, another device (e.g., remote device), or someother entity. A wireless node may provide, for example, connectivity foror to a network (e.g., a wide area network such as the Internet or acellular network) via a wired or wireless communication link. MTC UEs,as well as other UEs 120, may be implemented as Internet-of-Things (IoT)devices, e.g., narrowband IoT (NB-IoT) devices. In NB IoT, the UL and DLhave higher periodicities and repetitions interval values as a UE 120decodes data in extended coverage.

In FIG. 1 , a solid line with double arrows indicates desiredtransmissions between a UE 120 and a serving base station, which is abase station 110 designated to serve the UE 120 on the DL and/or UL. Adashed line with double arrows indicates interfering transmissionsbetween a UE 120 and a base station 110.

Certain wireless networks (e.g., LTE) utilize OFDM on the DL andsingle-carrier frequency division multiplexing (SC-FDM) on the UL. OFDMand SC-FDM partition the system bandwidth into multiple (K) orthogonalsubcarriers, which are also commonly referred to as tones, bins, etc.Each subcarrier may be modulated with data. In general, modulationsymbols are sent in the frequency domain with OFDM and in the timedomain with SC-FDM. The spacing between adjacent subcarriers may befixed, and the total number of subcarriers, K, may be dependent on thesystem bandwidth. For example, the spacing of the subcarriers may be 15kHz and the minimum resource allocation (called a ‘resource block’) maybe twelve (12) subcarriers (or one hundred eighty (180) kHz).Consequently, the nominal FFT size may be equal to one hundred andtwenty-eight (128), two hundred and fifty-six (256), five hundred andtwelve (512), one thousand twenty-four (1024), or two thousandforty-eight (2048) for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz,respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (e.g., six (6)resource blocks), and there may be 1, two (2), four (4), eight (8), orsixteen (16) subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR or other wirelesscommunications systems. NR may utilize OFDM with a CP on the UL and DLand may include support for half-duplex operation using time divisionduplex (TDD). A single component carrier bandwidth of one hundred (100)MHz may be supported. NR resource blocks may span 12 sub-carriers with asub-carrier bandwidth of seventy-five (75) kHz over a 0.1 milliseconds(ms) duration. Each radio frame may consist of fifty (50) subframes witha length of 10 ms. Consequently, each subframe may have a length of 0.2ms. Each subframe may indicate a link direction (e.g., DL or UL) fordata transmission and the link direction for each subframe may bedynamically switched. Each subframe may include DL/UL data as well asDL/UL control data. UL and DL subframes (e.g., for NR) may be describedin more detail with respect to FIGS. 6A, 6B, 7A, and 7B. Beamforming maybe supported and beam direction may be dynamically configured. MIMOtransmissions with precoding may also be supported. MIMO configurationsin the DL may support up to 8 transmit antennas with multi-layer DLtransmissions up to 8 streams and up to 2 streams per UE 120.Multi-layer transmissions with up to 2 streams per UE may be supported.Aggregation of multiple cells may be supported with up to 8 servingcells. Alternatively, NR may support a different air interface, otherthan an OFDM-based interface. NR networks may include entities suchcentral units (CUs) and/or distributed units (DUs).

In some aspects, access to the air interface may be scheduled, where ascheduling entity (e.g., a base station 110) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed furtherherein, the scheduling entity may be responsible for scheduling,assigning, reconfiguring, and releasing resources for one or moresubordinate entities. That is, for scheduled communication, subordinateentities utilize resources allocated by the scheduling entity. Basestations 110 are not the sole entities that may function as a schedulingentity. That is, in some aspects, a UE 120 may function as a schedulingentity, scheduling resources for one or more subordinate entities (e.g.,one or more other UEs 120). In this aspect, a first UE 120 isfunctioning as a scheduling entity, and other UEs 120 utilize resourcesscheduled by the first UE 120 for wireless communication. A UE 120 mayfunction as a scheduling entity in a peer-to-peer (P2P) network and/orin a mesh network. In a mesh network example, UEs 120 may optionallycommunicate directly with one another in addition to communicating withthe scheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

As discussed herein, a radio access network (RAN) may include a CU andone or more DUs. An NR base station (e.g., eNB, 5G Node B, Node B, TRP,AP, or gNB) may correspond to one or multiple base stations 110. NRcells may be configured as access cell (ACells) or data only cells(DCells). For example, the RAN (e.g., a CU or DU) may configure thecells. DCells may be cells used for carrier aggregation or dualconnectivity, but not used for initial access, cellselection/reselection, or handover. In some cases DCells may nottransmit synchronization signals (SS), and in other cases DCells maytransmit SS. NR base stations may transmit DL signals to UEs 120indicating the cell type. Based on the cell type indication, the UE 120may communicate with the NR base station. For example, the UE 120 maydetermine NR base stations to consider for cell selection, access,handover, and/or measurement based on the indicated cell type.

In some cases, the UEs 120 may be examples of vehicles operating withinthe wireless network 100. In these cases, the UEs 120 may detect otherUEs 120 and communicate with the other UEs 120 directly (e.g., with noor minimal communication with base stations 110). In some cases, a UE120 may transmit a radar waveform to detect nearby UEs 120. However, ifthese other UEs 120 also transmit radar waveforms to detect targetdevices, the multiple radar sources may result in interference and poordetection performance. To mitigate such issues, each UE 120 may transmitindications of the waveform parameters used by that UE 120, such thatthe nearby UEs 120 can identify the other radar waveforms and reduce theinterference caused by these radar waveforms.

FIG. 2 illustrates an example logical architecture of a distributed RAN200 in accordance with aspects of the present disclosure. Thedistributed RAN 200 may be implemented in the wireless communicationsystem illustrated in FIG. 1 . A 5G access node 206 may include anaccess node controller (ANC) 202. The ANC may be a CU of the distributedRAN 200. The backhaul interface to the next generation core network(NG-CN) 204 may terminate at the ANC 202. The backhaul interface toneighboring next generation access nodes (NG-ANs) 210 may terminate atthe ANC 202. The ANC 202 may include one or more TRPs 208 (which mayalso be referred to as base stations, NR base stations, Node Bs, 5G NBs,APs, eNBs, gNBs, or some other term). As described herein, a TRP 208 maybe used interchangeably with “cell.”

The TRPs 208 may be examples of DUs. The TRPs 208 may be connected toone ANC (e.g., ANC 202) or more than one ANC. For example, for RANsharing, radio as a service (RaaS), and service specific ANCdeployments, the TRP 208 may be connected to more than one ANC 202. ATRP 208 may include one or more antenna ports. The TRPs 208 may beconfigured to individually (e.g., in dynamic selection) or jointly(e.g., in joint transmission) serve traffic to a UE.

The local architecture may be used to illustrate fronthaul definition.The architecture may be defined such that it may support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE.According to aspects, the NG-AN 210 may support dual connectivity withNR. The NG-AN 210 may share a common fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 208. Forexample, cooperation may be preset within a TRP 208 and/or across TRPs208 via the ANC 202. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture. The Radio Resource Control (RRC)layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control(RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY)layers may be adaptably placed at the DU or CU (e.g., TRP 208 or ANC202, respectively). According to certain aspects, a base station mayinclude a CU (e.g., ANC 202) and/or one or more distributed units (e.g.,one or more TRPs 208). In some cases, the distributed RAN 200 maysupport systems containing multi-radar coexistence. In these cases, thedistributed RAN 200 may support the use of side-communication channelsfor exchanging radar information. The exchange of radar information mayallow for devices to select radar waveforms based on the radarinformation for other devices, allowing for improved multi-radarcoexistence between the devices.

FIG. 3 illustrates an example physical architecture of a distributed RAN300 in accordance with aspects of the present disclosure. A centralizedcore network unit (C-CU) 302 may host core network functions. The C-CU302 may be centrally deployed. C-CU 302 functionality may be offloaded(e.g., to advanced wireless services (AWSs)), in an effort to handlepeak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU 304 may host core network functions locally. TheC-RU 304 may have distributed deployment. The C-RU 304 may be closer tothe network edge.

A DU 306 may host one or more TRPs (e.g., edge nodes (ENs), edge units(EUs), radio heads (RHs), smart radio heads (SRHs), or the like). The DU306 may be located at edges of the network with RF functionality. Insome cases, the distributed RAN 300 may support devices using aside-communication channel for exchanging radar information to improvemulti-radar coexistence. In some cases, the distributed RAN 300 mayallow for centralized operation, where a DU 306 may transmit radarinformation to vehicles covered by the DU 306.

FIG. 4 illustrates example components of a base station 110 and a UE 120(e.g., as illustrated in FIG. 1 ) in a wireless communications system400 in accordance with aspects of the present disclosure. As describedherein, the base station 110 may include one or more TRP. One or morecomponents of the base station 110 and UE 120 may be used to practiceaspects of the present disclosure. For example, antennas 452, processors466, 458, 464, and/or controller/processor 480 of the UE 120 and/orantennas 434, processors 430, 420, 438, and/or controller/processor 440of the base station 110 may be used to perform the operations describedherein.

FIG. 4 shows a block diagram of a design of a base station 110 and a UE120, which may be one of the base stations and one of the UEs describedwith reference to FIG. 1 . For a restricted association scenario, thebase station 110 may be the macro base station 110 c in FIG. 1 , and theUE 120 may be the UE 120 y. The base station 110 may also be a basestation of some other type. The base station 110 may be equipped withantennas 434 a through 434 t, and the UE 120 may be equipped withantennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the Physical Broadcast Channel(PBCH), Physical Control Format Indicator Channel (PCFICH), PhysicalHybrid Automatic repeat request (ARQ) Indicator Channel (PHICH),Physical Downlink Control Channel (PDCCH), etc. The data may be for thePhysical Downlink Shared Channel (PDSCH), etc. The transmit processor420 may process (e.g., encode and symbol map) the data and controlinformation to obtain data symbols and control symbols, respectively.The processor 420 may also generate reference symbols, e.g., for theprimary synchronization signal (PSS), secondary synchronization signal(SSS), cell-specific reference signal, etc. A transmit (TX) MIMOprocessor 430 may perform spatial processing (e.g., precoding) on thedata symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. For example, the TX MIMO processor 430 mayperform certain aspects described herein for reference signal (RS)multiplexing. Each modulator 432 may process a respective output symbolstream (e.g., for OFDM, etc.) to obtain an output sample stream. Eachmodulator 432 may further process (e.g., convert to analog, amplify,filter, and upconvert) the output sample stream to obtain a DL signal.DL signals from modulators 432 a through 432 t may be transmitted viathe antennas 434 a through 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the DLsignals from the base station 110 and may provide received signals tothe demodulators 454 a through 454 r, respectively. Each demodulator 454may condition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain input samples. Each demodulator 454may further process the input samples (e.g., for OFDM, etc.) to obtainreceived symbols. A MIMO detector 456 may obtain received symbols fromall the demodulators 454 a through 454 r, perform MIMO detection on thereceived symbols if applicable, and provide detected symbols. Forexample, MIMO detector 456 may provide detected RS transmitted usingtechniques described herein. A receive processor 458 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providedecoded data for the UE 120 to a data sink 460, and provide decodedcontrol information to a controller/processor 480. According to one ormore cases, coordinated multi-point (CoMP) aspects can include providingthe antennas, as well as some Tx/receive (Rx) functionalities, such thatthey reside in DUs. For example, some Tx/Rx processing may be done inthe CU, while other processing can be done at the DUs. In accordancewith one or more aspects as shown in the diagram, the base stationMOD/DEMODs 432 may be in the DUs.

On the UL, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the Physical Uplink Shared Channel (PUSCH)) froma data source 462 and control information (e.g., for the Physical UplinkControl Channel (PUCCH)) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the base station 110. At the base station 110, the ULsignals from the UE 120 may be received by the antennas 434, processedby the modulators 432, detected by a MIMO detector 436 if applicable,and further processed by a receive processor 438 to obtain decoded dataand control information sent by the UE 120. The receive processor 438may provide the decoded data to a data sink 439 and the decoded controlinformation to the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect the processes for the techniques described herein. The processor480 and/or other processors and modules at the UE 120 may also performor direct processes for the techniques described herein. The memories442 and 482 may store data and program codes for the base station 110and the UE 120, respectively. A scheduler 444 may schedule UEs for datatransmission on the DL and/or UL.

While FIG. 4 illustrates communication between a base station 110 and aUE 120, in some systems UEs 120 may detect each other and transmitinformation directly to one another (e.g., over a side-communicationchannel). In these cases, the UEs 120 may detect other UEs 120 andcommunicate with the other UEs 120 directly (e.g., without thecommunication passing through or being relayed by a base station 110).In some cases, a UE 120 may transmit a radar waveform (e.g., using anantenna 452) to detect nearby UEs 120. To improve multi-radarcoexistence between the UEs 120, each UE 120 may transmit indications ofthe waveform parameters used by that UE 120, such that the nearby UEs120 can identify the other radar waveforms and reduce the interferencecaused by these waves. For example, a UE 120 may vary its waveformand/or waveform parameters for at least a subset of chirps based on theselected parameters for nearby UEs 120 to achieve interference shaping,suppression, or both. This may improve the reliability of the targetdetection procedure performed by the UE 120.

FIG. 5A illustrates an example of a DL-centric subframe 500A inaccordance with aspects of the present disclosure. The DL-centricsubframe 500A may include a control portion 502A. The control portion502A may exist in the initial or beginning portion of the DL-centricsubframe 500A. The control portion 502A may include various schedulinginformation and/or control information corresponding to various portionsof the DL-centric subframe 500A. In some configurations, the controlportion 502A may be a PDCCH, as indicated in FIG. 5A.

The DL-centric subframe 500A may also include a DL data portion 504A.The DL data portion 504A may sometimes be referred to as the payload ofthe DL-centric subframe 500A. The DL data portion 504A may include thecommunication resources utilized to communicate DL data from ascheduling entity 202 (e.g., eNB, base station, Node B, 5G NB, TRP, gNB,etc.) to a subordinate entity, e.g., a UE 120. In some configurations,the DL data portion 504A may be a PDSCH.

The DL-centric subframe 500A may also include a common UL portion 506A.The common UL portion 506A may sometimes be referred to as an UL burst,a common UL burst, and/or various other suitable terms. The common ULportion 506A may include feedback information corresponding to variousother portions of the DL-centric subframe 500A. For example, the commonUL portion 506 may include feedback information corresponding to thecontrol portion 502A. Non-limiting examples of feedback information mayinclude an acknowledgment (ACK) signal, a negative acknowledgment (NACK)signal, a hybrid automatic repeat request (HARQ) indicator, and/orvarious other types information. The common UL portion 506A may includeadditional or alternative information, such as information pertaining torandom access channel (RACH) procedures, scheduling requests (SRs),sounding reference signals (SRS), and various other suitable types ofinformation.

As illustrated in FIG. 5A, the end of the DL data portion 504A may beseparated in time from the beginning of the common UL portion 506A. Thistime separation may sometimes be referred to as a gap, a guard period(GP), a guard interval, and/or various other suitable terms. Thisseparation provides time for the switchover from DL communication (e.g.,reception operation by the subordinate entity, e.g., UE 120) to ULcommunication (e.g., transmission by the subordinate entity, e.g., UE120). One of ordinary skill in the art will understand, however, thatthe foregoing is merely one example of a DL-centric subframe 500A andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

FIG. 5B illustrates an example of an UL-centric subframe 500B inaccordance with aspects of the present disclosure. The UL-centricsubframe 500B may include a control portion 502B. The control portion502B may exist in the initial or beginning portion of the UL-centricsubframe 500B. The control portion 502B in FIG. 5B may be similar to thecontrol portion 502A described herein with reference to FIG. 5A. TheUL-centric subframe 500B may also include an UL data portion 504B. TheUL data portion 504B may sometimes be referred to as the payload of theUL-centric subframe 500B. The UL portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., a UE 120) to the scheduling entity 202 (e.g., a base station110). In some configurations, the control portion 502B may be a PUSCH.As illustrated in FIG. 5B, the end of the control portion 502B may beseparated in time from the beginning of the UL data portion 504B. Thistime separation may sometimes be referred to as a gap, GP, guardinterval, and/or various other suitable terms. This separation providestime for the switchover from DL communication (e.g., reception operationby the scheduling entity 202) to UL communication (e.g., transmission bythe scheduling entity 202).

The UL-centric subframe 500B may also include a common UL portion 506B.The common UL portion 506B in FIG. 5B may be similar to the common ULportion 506A described herein with reference to FIG. 5A. The common ULportion 506B may additionally or alternatively include informationpertaining to channel quality indicators (CQIs), SRSs, and various othertypes of information. One of ordinary skill in the art will understandthat the foregoing is merely one aspect of an UL-centric subframe 500Band alternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

As described herein, an UL-centric subframe 500B may be used fortransmitting UL data from one or more mobile stations to a base station,and a DL centric subframe may be used for transmitting DL data from thebase station to the one or more mobile stations. In one aspect, a framemay include both UL-centric subframes 500B and DL-centric subframes500A. In this aspect, the ratio of UL-centric subframes 500B toDL-centric subframes 500A in a frame may be dynamically adjusted basedon the amount of UL data and the amount of DL data to be transmitted.For example, if there is more UL data, then the ratio of UL-centricsubframes 500B to DL-centric subframes 500A may be increased.Conversely, if there is more DL data, then the ratio of UL-centricsubframes 500A to DL-centric subframes 500B may be decreased.

In some wireless communications systems, multiple radar sources may leadto significant interference. Conventional radar waveforms, such asfrequency-modulated continuous-wave (FMCW) radar, do not nativelysupport multiple access and thereby may be indistinguishable fromvarious sources (e.g., automobiles). Thus with multiple radar sources,it can be difficult to determine whether a reflection is from a detectedtarget or if it is interference from another radar source. For example,FMCW automotive radars may obtain range and velocity information fromthe beat frequency, which is composed of propagation delay and Dopplerfrequency. A Doppler frequency shift, f_(D)=2v/λ, is introduced by atarget which moves with velocity v with a radar wavelength λ. In themulti-radar coexistence scenario, the transmissions from other radarsources (e.g., automobiles) may appear as a ghost target which may beparticularly bothersome since it may appear in the same angulardirection as the desired reflected signal from that object (e.g., anautomobile) and may not be readily identifiable as a ghost or normal(desired) target. Furthermore, the direct signal from the radar sourcemay be significantly stronger than the reflected signal from the targetand may present a problem for the receiver to detect the weak reflectedsignals in the presence of strong interfering transmissions from otherradar sources. As such, a UE 120 transmitting the radar waveform mayfail to identify one or more nearby targets (e.g., based on theinterference from the direct radar signals transmitted by the target).

FIG. 6A illustrates an example wireless communications system 600A inaccordance with aspects of the present disclosure. The wirelesscommunications system 600A may include a vehicle 620 moving from left toright that emits radar. This vehicle 620 may be an example of a UE 120as described with reference to FIGS. 1 through 5 . The vehicle 620 mayencounter other UEs 120 (e.g., vehicles 625 and 630) moving from rightto left. Both vehicles 625 and 630 moving from right to left reflectback desired signals 610 and 615, respectively (e.g., based on the radaremitted by the car 620). The vehicle 630 moving from right to leftclosest to the vehicle 620 moving from left to right may also transmitsradar 605 or another type of signal which may act as interference to thevehicle 620 moving from left to right. If the vehicle 630 transmits aradar waveform, the vehicle 620 may not be able to distinguish theinterference caused by the radar waveform from a reflected signalindicating a nearby target (e.g., a nearby UE 120, vehicle, structure,interference source, etc.).

FIG. 6B illustrates an example graph 600B showing received power ofdirect and reflected signals over distance in accordance with aspects ofthe present disclosure. The graph 600B may illustrate the problem withinterference from direct signals, in that interference due to a directtransmission 617 is much stronger than the reflected signal from atarget 622. Axis 607 may represent a range of received power values (indBm) for the signals and axis 612 may represent distances from thesource (e.g., vehicle 620 emitting the radar) to the target (e.g.,vehicle 630). Interference may appear as a ghost target at half thedistance (e.g., plus a time offset) from the actual target and with ahigh power. With reflected signals from targets, the desired (i.e.,reflected) signals may have relatively low signal-to-interference ratios(SIRs) due to the near-far effect, the direct transmission 617 beingreceived at a much stronger power than the reflected (desired) signalfrom the target 622, or both. That is, the interference may have arelatively high power compared to the desired signals reflected from thetarget.

The graph 600B shows the received signal power from a reflected(desired) path based on a device (e.g., due to a radar transmission by afirst source device) and a direct (interfering) signal from a secondsource device, assuming the same transmit power at both radar sources.The reflected signal may decay by a factor of approximately 1/R⁴, whereR is the distance from the vehicle 630 reflecting the radar and thedirect, interference signal may decay by a factor of approximately 1/R²,where R is the distance from the vehicle 630 transmitting the direct,interference radar signal. Thus, based on the example illustrated inFIGS. 6A and 6B, the reflected signal 622 from a desired target 625 at adistance 635 away (e.g., one hundred fifty (150) meters (m) away fromthe source vehicle 620) may be weaker than a direct interfering signalfrom a nearby source 630 at a distance 640 away (e.g., 10 m) and maypresent a challenging environment for target detection. Note that, insome scenarios, some spatial rejection is possible to mitigate thenear-far effect and depends on the geometry (e.g., location of desiredradar source, target, interfering radar source, etc.) and spatialresponse of the radar receiver antennas. However, such a spatialrejection may not always occur. For example, cases where the three carsin FIG. 6A are on (or close to) a straight line to have no (or small)angular difference between the two radio paths (desired radar to thetarget vs. desired radar to the interfering radar) may not alwaysinclude spatial rejection.

The present method, apparatuses, and non-transitory processor-readablestorage medium may enable multi-channel coexistence usingside-communication channels. In one aspect, an FMCW waveform is used. Insome cases, including for automobiles, the FMCW is the most commonlyused waveform. However, the present operations apply to other radarwaveforms as well. With FMCW, the frequency of the waveform is variedlinearly with time as a sawtooth or triangle shaped function. A vehicle620 transmitting the radar waveform may receive and process reflectedsignals from target(s) and detect the range and Doppler of each targetbased on the difference in the received the transmitted frequencies.

In FMCW, the radar waveform may include a set of chirps, where eachchirp has a specific chirp duration. A modulating signal may vary achirp's instantaneous frequency linearly over a fixed period of time(e.g., sweep time T_(C)) in a transmission. The transmitted signal(e.g., the emitted radar waveform) may interact with the target andreflect back to a receive antenna. The frequency difference, Δf, betweenthe transmitted signal and the received signal may increase with thedelay of receiving the reflected signal. The distance of the target fromthe radar is the range, and the delay r is linearly proportional to therange between the target and the source and is equal to the round triptravel time. The echo from the target may then be mixed with thetransmitted signal and down-converted to produce a beat signal which maybe linearly proportional to the range between the target and the sourceof the signal after demodulation. FIG. 8 illustrates an FMCW system 800with received and transmitted ramp waveforms with sawtooth chirpmodulation in accordance with aspects of the present disclosure. Axis805 may represent frequency, and axis 810 may represent time. Timeinterval 815 may represent the delay, τ. Frequency interval 820 mayrepresent the frequency difference, Δf, between the transmitted signal(represented by 830) and the received signal (represented by 835).Frequency interval 825 may be a frequency range, B, for the chirps.

The parameters of the FMCW waveform can vary for one or more chirps(e.g., every chirp) for interference randomization. Interferencesuppression and interference shaping may be possible based on UEs 120(e.g., vehicles) selecting patterns based on which parameters are variedacross users. FIGS. 7A and 7B illustrate frequency-time plots 700 of anFMCW with different parameters in accordance with aspects of the presentdisclosure. In the frequency-time plots 700A and 700B, B may representthe frequency range 705 or 707 for the FMCW and T_(C) may represent theduration of a chirp (shown in time 710 and 712). The frequency of thewave sweeps across the entire bandwidth part from zero (0) to B (where 0and B illustrate the range of the frequency, and the actual frequencyvalues may be any values in the bandwidth). Typically, the frequency ofthe radar may sweep from 1 to 2 GHz. The chirp period may typically spanbetween 10 to two hundred (200) micro-seconds.

FIG. 7A may illustrate unvaried waveform parameters for an FMCWwaveform. In the example of FIG. 7A and frequency-time plot 700A, 705may represent B, 710 may represent a time including N_(C) chirps, andeach of 715 may represent a chirp duration T_(C). FIG. 7B may illustratevariations in the slope β and/or the frequency offset f₀ parameters(e.g., where the variations may be performed based on radar informationfor nearby vehicles in order to support interference shaping,suppression, or both). In the example of FIG. 7B and graph 700B, 707 mayrepresent B, 712 may represent a time including N_(C) chirps, and eachof 717 may represent a chirp duration T_(C) (or may represent areference chirp duration T_(C)). In some cases, multiple chirps may betransmitted back to back. At the receiver, multiple chirps may beprocessed (e.g., in sequence). In some cases (e.g., as illustrated), thechirp duration T_(C) may stay the same for a radar waveform, and thefrequency of the wave may sweep through the frequency range B any numberof times within the reference chirp duration. In other cases, the chirpduration T_(C) may correspond to a single frequency sweep through thefrequency range B, and, accordingly, the chirp duration T_(C) may varyfor a set of chirps depending on the slope, β. For a “fast” chirp, theT_(C) duration is short, and for a “slow” chirp, the T_(C) duration islong. In some cases, a UE 120 (e.g., a vehicle) may select waveformparameters for transmission of the radar waveform, where the waveformparameters are applied to frequency-time plot 700A. The UE may varythese selected waveform parameters for at least one chirp, resulting inselected waveform parameters corresponding to frequency-time plot 700B.

The system may be configured to determine how much to vary the chirpparameters. Two parameters which define the waveform used over the chirpduration T_(C) may be the slope, β, and the frequency offset, f₀, wherethe slope is defined as β=B/T_(C) for a specific chirp. For example, anFMCW radar system can be designed to sweep the frequency linearly over 1GHz and 50 us, yielding a slope β=1 GHz/50 us, and the frequency offsetf₀ can be set to any value between 0 to 1 GHz. The frequency offset f₀may correspond to the initial frequency value at the start of the chirpduration T_(C). In FIG. 7A, the slope and frequency offset may be keptconstant over multiple chirps. That is, B 705 may be the same for eachchirp of a set of chirps and T_(C) 715 a, 715 b, and 715 c may be thesame for the set of chirps, resulting in a constant slope β for the setof chirps. Additionally, the frequency offset, f₀, may be the same foreach chirp of the set of chirps. In FIG. 7B, instead of keeping theparameters constant, a UE (e.g., a vehicle in a vehicle-to-everything(V2X) system) may vary the parameters determining the frequency of thechirps. Furthermore, if a pattern is selected to vary the slope and thefrequency offset for at least one chirp (e.g., per chirp), interferencefrom other radar emissions may be suppressed or shaped (e.g., offset)based on the varied waveform parameters. Based on the way parameters arevaried between different radar sources, two effects may occur. In afirst aspect, interference between the radar sources may be suppressed.Additionally or alternatively, in a second aspect, interference may beshaped. Shaping the interference may involve time delaying and/orfrequency shifting the interference beyond what can be detected by thereceiver. By specifically selecting the parameters of the waveforms, thewaveforms of coexistent radar may be normalized so they do not mutuallyinterfere in a manner that affects the target detection performance.

In one aspect, certain choices of parameters of the FMCW waveform canlead to the radar waveform resembling a Zadoff-Chu sequence, whichexhibits correlation properties (e.g., autocorrelation,cross-correlation, etc.) which may help with interference suppression.

As discussed earlier, two parameters that can be varied from chirp tochirp are the slope β and the frequency offset f₀. In the equationsdescribed herein, the slope and frequency of the chirp may be determinedusing two parameters (u, q) for a given chirp.

In the equations described herein, the slope for chirp m may bedetermined as

$\beta^{(m)} = {u^{(m)}*\frac{B}{T_{c}}}$and the frequency offset may be determined as

$f_{0}^{(m)} = {u^{(m)}*\frac{( {1 + {2q^{(m)}}} )}{T_{c}}}$where m=1, 2, 3, . . . is the chirp index, T_(C) is the period of thechirp, B is the frequency range, and (u^((m)), q^((m))) are the twoparameters for the m^(th) chirp that determine the FMCW waveform suchthat is it resembles a Zadoff-Chu sequence. Using this result, theparameters (u^((m)), q^((m))) can be chosen at a UE 120 such thatinterference between coexistent radar will be suppressed by utilizingthe correlation properties of Zadoff-Chu waveforms. An equationdescribing both parameters for a set of chirps may be:

$\begin{matrix}{{( {\beta^{(m)},\; f_{0}^{(m)}} ) = ( {{u^{(m)}\frac{B}{T_{c}}},{u^{(m)}\frac{( {1 + {2q^{(m)}}} )}{T_{c}}}} )},} & (1)\end{matrix}$where T_(C) is the period of the chirp, B is the frequency range,β^((m)) is the slope and f₀ ^((m)) is the frequency offset, and(u^((m)), q^((m))) are the two parameters for the m^(th) chirp thatdetermine the FMCW waveform. The Zadoff-Chu sequence is an example of acomplex-valued mathematical sequence. It gives rise to anelectromagnetic signal of constant amplitude when it is applied to radiosignals, whereby cyclically shifted versions of the sequence imposed ona signal result in zero correlation with one another at the receiver.The “root sequence” is a generated Zadoff-Chu sequence that has not beenshifted. These sequences exhibit a property that cyclically shiftedversions of itself are orthogonal to one another, provided that eachcyclic shift, when viewed within the time domain of the signal, isgreater than the combined multi-path delay-spread and propagation delayof that signal between the transmitter and receiver.

In some cases, u_(i) ^((m))≠u_(j) ^((m)) where (.)^((m)) is the m^(th)chirp and i and j are two radar transmitters (e.g., for two UEs 120 withclose proximity of each other). In this case, the Zadoff Chu sequencesfor these radar transmitters may have cross-correlation, effectivelyraising the noise floor for interference. Here, two users (e.g.,corresponding to radar transmitters i and j) use different slopes, u_(i)^((m)) and u_(j) ^((m)), on the m^(th) chirp. This may lead to across-correlation of the corresponding sequences for i and j, which maybe limited by the length of the Zadoff Chu sequence. Thecross-correlation may result in interference suppression amongst the twoZadoff Chu sequences. The correlation amongst the two Zadoff Chusequences may raise the noise floor (e.g., meaning the two sequences arenot orthogonal). In these cases, the cross-correlation may be relativelysmall (but non-zero), meaning the interference may be spread with a lowenergy appearing as noise. This interference can be suppressed by thelength of the Zadoff-Chu sequences. Accordingly, the interference maynot appear as a ghost target but as suppressed noise (e.g., due to theinterference suppression) which raises the noise floor.

A UE (e.g., a vehicle) may shape interference by setting frequencyoffsets such that ghost targets or interference peaks appear beyond arange of interest. For example, if u_(i) ^((m))=u_(j) ^((m)) (e.g., theslope of the transmitter, i, for the m^(th) chirp is equal to the slopeof the transmitter, j, for the m^(th) chirp), the peak interference maybe shifted relative to (q_(i) ^((m))−q_(j) ^((m))) (e.g., the frequencyoffset parameter of the transmitter, i, for the m^(th) chirp minus thefrequency offset parameter of the transmitter, j, for the m^(th) chirp.In one aspect, the peak interference can be shifted to be greater thanthe range of interest. For example, for a range target (e.g., a range ofinterest) of 150 m, bandwidth of 1 GHz, chirp duration T_(C) of 10micro-seconds, slope parameter u_(i) ^((m))=u_(j) ^((m))=1, and areceiver with sampling rate of 1 giga samples per second (Gsps), (q_(i)^((m))−q_(j) ^((m))) can be set between [1000, 9000] such that mutualinterference will appear at a distance greater than 150 m which may bebeyond the range expected from any target reflected signals by design.So if the slopes u^((m)) for radar transmitters i and j are the sameslope size, the frequency offsets q_(i) ^((m)) and q_(j) ^((m)) can beselected so the peak of the interference can be shifted beyond apre-defined or dynamically determined range of interest. In one aspect,even if the radar transmitters are next to each other (e.g., within veryclose proximity), the energy from each radar transmitter will appear farfrom the other transmitter and not as interference within the range ofinterference based on the interference shaping techniques.

In a phase-coded FMCW system, avoiding coherent addition of chirps withthe same parameters helps suppress interference. For example, 90% of thechirps in a set of waveforms may be orthogonal, i.e., the parameters foreach chirp were selected such that interference between chirps ofdifferent waveforms are suppressed or shaped. However, 10% of the chirpsmay still have the same parameters across waveforms and therefore mayadd up coherently. A phase code can be added over a waveform to suppressor shape interference, such that each chirp of a set of chirps (e.g.,every chirp in a waveform) has an associated phase, where the phase mayvary from one chirp to another. The following Zadoff-Chu sequenceillustrates an example where a phase sequence is applied:

$\begin{matrix}{{x\lbrack {m,n} \rbrack} = {x_{FMCW}\lbrack {m,n} \rbrack}^{{- j}\;\pi\;\overset{\_}{u}\frac{{({m + 1 + {2\overset{\_}{q}}})}m}{N}}} & (2)\end{matrix}$In this case, m is the chirp index, with m=0, 1, . . . N, N is thenumber of chirps (e.g., the length of the Zadoff Chu sequence), and n isthe sample index within the m^(th) chirp. The phase modulation appliedmay be based on the Zadoff Chu sequence and determined by a choice ofthe parameters (u, q). By adding the phase code, there are, in effect,two nested Zadoff-Chu sequences. First, for the original FMCW waveformselected by the UE 120, every chirp resembles a Zadoff-Chu sequence witha certain choice of parameters. Second, the UE 120 implements aZadoff-Chu sequence representing phase modulation for the waveform.

The processing on the receiver end may also change to coherently combinedesired signals. For example, a receiver may use equalization,resampling, or some combination of these or other techniques forcoherently combining desired signals on the receiver side.

From the equations described herein, the following set of parameters canbe used to vary an FMCW waveform for a set of chirps (e.g., every chirp)for interference randomization:{ū _(i) ,q _(i) ,c _(i):=(u _(i) ^((m)) ,q _(i) ^((m))),m=1, . . . ,N_(C)},  (3)where i is the transmitter index, m is the chirp index, N_(C) is thetotal number of chirps over which randomization is performed, (ū_(i), q_(i)) control the phase-modulation applied across N_(C) chirps, and(u_(i) ^((m)), q_(i) ^((m))) determine the slope and frequency offset ofthe FMCW waveform in the m^(th) chirp. For example, a UE 120 may selecta codeword from a codebook, where the codeword indicates the parametersto use for the waveform. Multiple users may use a same codebook forcodebook-based selection of the FMCW parameters. In some cases, the UE120 may select (ū_(i), q _(i),) (e.g., randomly, pseudo-randomly, basedon some procedure, etc.) with a uniform distribution within a range. TheUE 120 may additionally or alternatively select c_(i):=(u_(i)(m), q_(i)^((m))), m=1, . . . , N_(C)} such that a “distance” among codewords(e.g., codewords selected by nearby UEs 120) is maximized. The“distance” measurement may be set to a maximum distance if the slopesfor chirps are different, while the “distance” measurement may be setproportional to (q_(i)−q_(k)) if the slopes are the same (e.g., wherethe distance may top out at the maximum distance if q_(i)−q_(k)>maxdelay).

When automobiles are in traffic, these parameters can be chosen from acodebook that includes of a set of allowed patterns of parameter values(e.g., codewords). The codebook can be designed to yield low mutualinterference among any two codewords. Thus, codebook-based selection ofwaveform parameters can be done for multiple users to have low mutualinterference in the system.

If the pattern of parameters (e.g., codeword) that another vehicle withtransmitter j is using is known by the vehicle with transmitter i, thenthe vehicle with transmitter i can select a codeword which may yield theleast (or relatively small) mutual interference to the pattern used bythe vehicle with transmitter j. In one aspect, the vehicle withtransmitter i may determine the set of patterns being used by othervehicles in proximity. The vehicle with transmitter i may select acodeword for its own transmission that leads to the least mutualinterference with the determined set of patterns for the other vehicles.In some cases, a side-communication channel can be used to communicatethe pattern being used by the vehicle, and the nearby vehicles canlisten to (e.g., monitor for) such broadcast messages to determine theset of codewords being used in a certain proximity (e.g., within acertain distance range, within a range of detection, etc.). Determiningthe codewords used by nearby UEs 120 (e.g., vehicles) based onside-communication channel transmissions may support a low computationalcomplexity.

To indicate a specific codeword selected from a codebook includingmultiple possible codewords, a UE 120 may broadcast an indication of theselected codeword for reception by nearby UEs 120. For example, afterselecting a pattern of waveform parameters, the UE 120 may use aside-communication channel to broadcast the pattern being used for aradar waveform. For a pattern of parameters used over a set of chirps(e.g., a codeword), the pattern of parameters may be chosen from a setof patterns (e.g., a codebook of patterns). In some cases, theparameters may be selected from a codebook containing all supportedpatterns of parameters. In these cases, the selected pattern can beidentified by an index specified in the codebook (e.g., instead of beingidentified based on all of the parameters in the pattern). Transmittingan index indicating the codeword, as opposed to values for all of theparameters specified by the codeword, may significantly reduce thepayload size and overhead of the side-communication channeltransmission.

A side channel (e.g., a V2X communication channel or cellularcommunications) may be used to communicate the vehicle's location andthe parameter pattern (or codeword) being used. Centralized (e.g., basestation-based) and/or decentralized (e.g., vehicle-to-vehicle-based)methods can be used to gather information about the codewords (e.g., thepatterns of parameters used over chirps) being used in a car'sproximity. In a centralized operation, a UE 120 may receive informationabout the codewords being used near the UE 120 (e.g., with a certainrange threshold) from a base station 110. In a decentralized operation,the UE 120 may receive information about codewords being used near theUE 120 from the other UEs 120 near the UE 120 (e.g., overside-communication channels). For example, each UE 120 may broadcast anindication of its own selected waveform parameters for reception byother UEs monitoring for side channel transmissions. Interferencecancellation and selection of a vehicle's own codeword can be done basedon this side information. A UE 120 can select a pattern that is mostorthogonal to (e.g., causes the least interference to) the patterns usedby other UEs 120 in its vicinity since all the cars in its vicinity arebroadcasting their patterns. With the centralized V2X (C-V2X) mode ofoperation, there may be two sidelink (or side-communication) channels.One is the physical side link shared channel (PSSCH), which may be usedto send and receive data, and the other is the physical side linkcontrol channel (PSCCH), which may be used to send and receive controlsignaling related to the associated PSSCH channel.

Radar target detection includes transmitting a radar waveform includingN_(C) chirps, where each chirp has a duration T_(C) (which may be thesame for all chirps or different for one or more chirps in thewaveform). In one aspect, every chirp uses a FMCW waveform. In anotheraspect, every chirp uses a phase-coded FMCW waveform. In another aspect,at least one chirp uses a FMCW waveform or a phase-coded FMCW waveform.To suppress interference, the waveform and/or waveform parameters may bevaried for at least a subset of the N_(C) chirps. In one aspect, theparameters being varied are determined from a set of possible patterns(e.g., codewords), where a pattern is a codeword and a set of patternsis a codebook. In one aspect, the UE may broadcast its codeword over aside-channel or side-communication channel.

A UE 120 (e.g., a vehicle) may use the side information (e.g., thebroadcast information) received from other vehicles indicating theparameter pattern (or codeword) being used by the other vehicles, thelocations of the other vehicles, the location of the UE 120, or somecombination of this information to determine the set of codewords beingused in the proximity of the UE 120 (e.g., according to some proximitythreshold or definition). In one case, the information of the set ofcodewords being used in the proximity of the UE 120 is conveyed to theUE 120 (e.g., an automobile) by direct communication with a networkentity (e.g., a base station 110, or roadside unit (RSU), or another UE120).

In one case, the UE 120 may broadcast a signal (e.g., a beacon, a codeddiscovery message, etc.) on a side-channel to announce its presence.This message may contain only a subset of the information (e.g., themessage may or may not indicate the selected waveform parameters), butserves as an indication that a vehicle is present and activelytransmitting radar waveforms. The nearby vehicles receiving this messagecan utilize this information to estimate the waveform parameters beingused by those nearby vehicles.

RSUs may be examples of radio base stations installed along the side ofthe road or at intersections. For example, they can be on traffic lightpoles, lamp poles, electronic toll collectors, etc. The messagetransmitted may have a common or dynamically determined transport block(TB) size, which may represent the size of the message in physicalresource blocks (PRBs).

FIG. 9 is a flowchart illustrating a method for enabling the coexistenceof multiple radar sources by a UE, where the UE may suppress radarinterference in a communication system in accordance with aspects of thepresent disclosure. In step 910, the UE may choose patterns (e.g., apattern of waveform parameters, a codeword, etc.) based on whichparameters are varied across users. The UE may determine the parametersvaried across nearby users based on receiving one or more transmissionsindicating this information (e.g., from a centralized base station orbroadcast by nearby UEs). In step 920, the UE may select waveformparameters based on one or more codebooks. In step 930, the UE may varywaveform parameters in at least one chirp of the set of chirpscorresponding to the waveform. In step 940, the UE may set frequencyoffsets such that interference peaks for one or more nearby UEs appearbeyond a range of interest. In step 945, the UE may add a phase code tothe waveform. Step 950 involves the UE broadcasting the selected patternbeing used (e.g., after performing one or more of the above operations)using a side-communication channel. In some cases, following theselection process, the UE may transmit (e.g., emit) the determined radarwaveform for target detection.

FIG. 10 is a flowchart illustrating a method for enabling thecoexistence of multiple radar sources by UEs including suppressing radarinterference in a communication system in accordance with aspects of thepresent disclosure. In step 1010, a UE may select waveform parametersbased on codebooks (e.g., according to a set of codewords received forthe UEs within a certain proximity of the UE). In step 1020, the UE maychoose a pattern of waveform parameters from a codebook of patterns. Instep 1030, the UE may use a side-communication channel to broadcast theselected pattern of waveform parameters being used. In step 1040, the UEmay receive information indicating a set of codewords being used in theproximity of the UE (e.g., by direct or relayed communication with anetwork entity). Step 1050 involves the UE broadcasting a signal such asa beacon or a coded discovery message using a side-communication channel(e.g., to indicate the presence and/or location of the UE).

FIG. 11 illustrates certain components that may be included within abase station 1101. The base station 1101 may be an access point, aNodeB, an evolved NodeB, etc. The base station 1101 includes a processor1103. The processor 1103 may be a general purpose single-chip ormulti-chip microprocessor (e.g., an advanced reduced instruction setcomputer (RISC) machine (ARM) microprocessor), a special purposemicroprocessor (e.g., a digital signal processor (DSP)), amicrocontroller, a programmable gate array, etc. The processor 1103 maybe referred to as a central processing unit (CPU). Although just asingle processor 1103 is shown in the base station 1101 of FIG. 11 , analternative configuration may include a combination of processors (e.g.,an ARM and a DSP).

The base station 1101 also includes memory 1105. The memory 1105 may beany electronic component capable of storing electronic information. Thememory 1505 may be embodied as random-access memory (RAM), read-onlymemory (ROM), magnetic disk storage media, optical storage media, flashmemory devices in RAM, on-board memory included with the processor,erasable programmable ROM (EPROM), electrical erasable programmable ROM(EEPROM), registers, and so forth, including combinations thereof.

Data 1107 and instructions 1109 may be stored in the memory 1105. Theinstructions 1109 may be executable by the processor 1103 to implementthe methods disclosed herein. Executing the instructions 1109 mayinvolve the use of the data 1107 that is stored in the memory 1105. Whenthe processor 1103 executes the instructions 1109, various portions ofthe instructions 1109 a may be loaded onto the processor 1103, andvarious pieces of data 1107 a may be loaded onto the processor 1103.

The base station 1101 may also include a transmitter 1111 and a receiver1113 to allow for transmission and reception of signals to and from thewireless device 1101. The transmitter 1111 and receiver 1113 may becollectively referred to as a transceiver 1115. Multiple antennas 1117(e.g., antennas 1117 a and 1117 b) may be electrically coupled to thetransceiver 1115. The base station 1101 may also include multipletransmitters, multiple receivers and/or multiple transceivers (notshown).

The various components of the base station 1101 may be coupled togetherby one or more buses, which may include a power bus, a control signalbus, a status signal bus, a data bus, etc. For the sake of clarity, thevarious buses are illustrated in FIG. 11 as a bus system 1119. AlthoughFIGS. 9 and 10 are discussed herein with reference to a UE, it should beunderstood that a base station, such as base station 1101, may performthe corresponding transmitting that is monitored and received by the UEas well as the receiving of the information indicated by the UEdiscussed in FIGS. 9 and 10 . These operations may be implemented inhardware or software executed by a processor like the processor 1103described with reference to FIG. 11 .

FIG. 12 illustrates certain components that may be included within awireless communication device 1201. The wireless communication device1201 may be an access terminal, a mobile station, a UE, etc. Thewireless communication device 1201 includes a processor 1203. Theprocessor 1203 may be a general-purpose single-chip or multi-chipmicroprocessor (e.g., an ARM), a special purpose microprocessor (e.g., aDSP), a microcontroller, a programmable gate array, etc. The processor1203 may be referred to as a CPU. Although just a single processor 1203is shown in the wireless communication device 1201 of FIG. 12 , in analternative configuration, a combination of processors (e.g., an ARM andDSP) could be used.

The wireless communication device 1201 also includes memory 1205. Thememory 1205 may be any electronic component capable of storingelectronic information. The memory 1205 may be embodied as RAM, ROM,magnetic disk storage media, optical storage media, flash memory devicesin RAM, on-board memory included with the processor, EPROM, EEPROM,registers, and so forth, including combinations thereof.

Data 1207 and instructions 1209 may be stored in the memory 1205. Theinstructions 1209 may be executable by the processor 1203 to implementthe methods disclosed herein. Executing the instructions 1209 mayinvolve the use of the data 1207 that is stored in the memory 1205. Whenthe processor 1203 executes the instructions 1209, various portions ofthe instructions 1209 a may be loaded onto the processor 1203, andvarious pieces of data 1207 a may be loaded onto the processor 1203.

The wireless communication device 1201 may also include a transmitter1211 and a receiver 1213 to support transmission and reception ofsignals to and from the wireless communication device 1201. Thetransmitter 1211 and receiver 1213 may be collectively referred to as atransceiver 1215. Multiple antennas 1217 (e.g., antennas 1217 a and 1217b) may be electrically coupled to the transceiver 1215. The wirelesscommunication device 1201 may also include multiple transmitters,multiple receivers and/or multiple transceivers (not shown).

The various components of the wireless communication device 1201 may becoupled together by one or more buses, which may include a power bus, acontrol signal bus, a status signal bus, a data bus, etc. For the sakeof clarity, the various buses are illustrated in FIG. 12 as a bus system1219. The wireless communication device 1201 may perform one or more ofthe operations described herein with reference to FIGS. 9 and 10 . Itshould be noted that these methods describe possible implementation, andthat the operations and the steps may be rearranged or otherwisemodified such that other implementations are possible. In some aspects,aspects from two or more of the methods may be combined. For example,aspects of each of the methods may include steps or aspects of the othermethods, or other steps or techniques described herein. Thus, aspects ofthe disclosure may provide for receiving on transmit resources oroperations and transmitting on receive resources or operations. Thefunctions described herein in the flowcharts of FIGS. 9 and 10 may beimplemented in hardware or software executed by a processor like theprocessor 1203 described with reference to FIG. 12 .

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different PHYlocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more”) indicates an inclusive listsuch that, for example, a list of at least one of A, B, or C means A orB or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media caninclude RAM, ROM, EEPROM, compact disk (CD) ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother non-transitory medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the herein are also included within the scope ofcomputer-readable media.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as (Global System forMobile communications (GSM)). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (wireless fidelity (Wi-Fi)), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and evolved UTRA (E-UTRA) are part ofUniversal Mobile Telecommunications system (Universal MobileTelecommunications System (UMTS)). 3GPP LTE and LTE-advanced (LTE-A) arenew releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-a,and GSM are described in documents from 3GPP. CDMA2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the systems and radio technologies mentioned herein as well asother systems and radio technologies. The description herein, however,describes an LTE system for purposes of example, and LTE terminology isused in much of the description, although the techniques are applicablebeyond LTE applications.

In LTE/LTE-A networks, including networks described herein, the term eNBmay be generally used to describe the base stations. The wirelesscommunications system or systems described herein may include aheterogeneous LTE/LTE-A network in which different types of eNBs providecoverage for various geographical regions. For example, each eNB or basestation may provide communication coverage for a macro cell, a smallcell, or other types of cell. The term “cell” is a 3GPP term that can beused to describe a base station, a carrier or component carrier (CC)associated with a base station, or a coverage area (e.g., sector, etc.)of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an AP, a radiotransceiver, a NodeB, eNodeB, Home NodeB, a Home eNodeB, or some othersuitable terminology. The geographic coverage area for a base stationmay be divided into sectors making up a portion of the coverage area.The wireless communications system or systems described herein mayinclude base stations of different types (e.g., macro or small cell basestations). The UEs described herein may be able to communicate withvarious types of base stations and network equipment including macroeNBs, small cell eNBs, relay base stations, and the like. There may beoverlapping geographic coverage areas for different technologies. Insome cases, different coverage areas may be associated with differentcommunication technologies. In some cases, the coverage area for onecommunication technology may overlap with the coverage area associatedwith another technology. Different technologies may be associated withthe same base station, or with different base stations.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The DL transmissions described herein may also be called forward linktransmissions while the UL transmissions may also be called reverse linktransmissions. Each communication link described herein including, forexample, wireless communications system 100 of FIG. 1 may include one ormore carriers, where each carrier may be a signal made up of multiplesub-carriers (e.g., waveform signals of different frequencies). Eachmodulated signal may be sent on a different sub-carrier and may carrycontrol information (e.g., reference signals, control channels, etc.),overhead information, user data, etc. The communication links describedherein may transmit bidirectional communications using frequencydivision duplex (FDD) (e.g., using paired spectrum resources) or TDDoperation (e.g., using unpaired spectrum resources). Frame structuresmay be defined for FDD (e.g., frame structure type 1) and TDD (e.g.,frame structure type 2).

Thus, aspects of the disclosure may provide for receiving on transmitand transmitting on receive. It should be noted that these methodsdescribe possible implementations, and that the operations and the stepsmay be rearranged or otherwise modified such that other implementationsare possible. In some aspects, aspects from two or more of the methodsmay be combined.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices(e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration). Thus, the functions describedherein may be performed by one or more other processing units (orcores), on at least one integrated circuit (IC). In various aspects,different types of ICs may be used (e.g., Structured/Platform ASICs, anFPGA, or another semi-custom IC), which may be programmed in any mannerknown in the art. The functions of each unit may also be implemented, inwhole or in part, with instructions embodied in a memory, formatted tobe executed by one or more general or application-specific processors.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

What is claimed is:
 1. A method for suppressing interference implementedby a user equipment (UE) with a radar in a communication system,comprising: selecting waveform parameters for transmission of a radarwaveform, the waveform parameters being a slope, a frequency offset, achirp duration, or a combination thereof of a chirp of the radarwaveform, wherein the radar waveform comprises a plurality of chirps andthe selecting comprises varying the waveform parameters for at least onechirp of the plurality of chirps; transmitting an indication of one ormore of the selected waveform parameters over the communication system;and transmitting the radar waveform according to the selected waveformparameters.
 2. The method of claim 1, wherein the selecting the waveformparameters comprises: selecting a codeword from a codebook comprising aplurality of codewords, wherein the codeword indicates the selectedwaveform parameters.
 3. The method of claim 2, wherein the selecting thewaveform parameters comprises: identifying a set of codewords foradditional UEs within a threshold distance; and varying the waveformparameters for the at least one chirp with uniform distribution within arange such that a distance is maximized between the selected codewordand the identified set of codewords.
 4. The method of claim 1, whereinthe transmitting the indication of the one or more of the selectedwaveform parameters comprises: broadcasting the indication of the one ormore of the selected waveform parameters on one or moreside-communication channels between the UE and one or more additionalUEs.
 5. The method of claim 1, wherein the transmitting the indicationof the one or more of the selected waveform parameters comprises:transmitting the indication of the one or more of the selected waveformparameters on an uplink channel between the UE and a network entity. 6.The method of claim 1, further comprising: receiving, from a networkentity, information of a set of codewords being used in proximity to theUE.
 7. The method of claim 1, further comprising: broadcasting a beacon,a coded discovery message, or a combination thereof on one or moreside-communication channels between the UE and one or more additionalUEs to indicate a location of the UE.
 8. The method of claim 1, furthercomprising: receiving information of a set of codewords used byadditional UEs on one or more side-communication channels between the UEand one or more of the additional UEs, wherein the waveform parametersare varied based at least in part on the information of the set ofcodewords used by the additional UEs.
 9. The method of claim 8, furthercomprising: receiving a set of beacons, a set of coded discoverymessages, or a combination thereof for the additional UEs on the one ormore side-communication channels between the UE and the one or more ofthe additional UEs to indicate locations of the additional UEs; anddetermining a set of proximity values for the additional UEs withrespect to the UE, wherein the waveform parameters are varied based atleast in part on the set of proximity values for the additional UEs. 10.The method of claim 1, further comprising: identifying, for the radarwaveform, a range of interest for interference sources; and setting afirst frequency offset for the radar waveform such that an interferencepeak of at least one interference source appears beyond the range ofinterest.
 11. The method of claim 1, further comprising: phase-codingone or more chirps of the radar waveform to avoid coherent addition ofchirps with other radar waveforms in the communication system.
 12. Themethod of claim 1, wherein each of the plurality of chirps sweeps acrossa frequency range at least once during a respective chirp duration. 13.The method of claim 1, wherein selecting the waveform parameterscomprises selecting values for at least two of the waveform parametersfor each of the plurality of chirps.
 14. The method of claim 13, whereinthe at least two of the waveform parameters comprise the slope and thefrequency offset.
 15. The method of claim 1, wherein selecting thewaveform parameters comprises selecting a first slope and a firstfrequency offset for one or more first chirps of the plurality of chirpsand selecting a second slope and a second frequency offset for one ormore second chirps of the plurality of chirps.
 16. An apparatus forsuppressing interference implemented by a user equipment (UE) with aradar in a communication system, comprising: means for selectingwaveform parameters for transmission of a radar waveform, the waveformparameters being a slope, a frequency offset, a chirp duration, or acombination thereof of a chirp of the radar waveform, wherein the radarwaveform comprises a plurality of chirps and the selecting comprisesvarying the waveform parameters for at least one chirp of the pluralityof chirps; means for transmitting an indication of one or more of theselected waveform parameters over the communication system; and meansfor transmitting the radar waveform according to the selected waveformparameters.
 17. The apparatus of claim 16, wherein the means forselecting the waveform parameters comprises: means for selecting acodeword from a codebook comprising a plurality of codewords, whereinthe codeword indicates the selected waveform parameters.
 18. Theapparatus of claim 17, wherein the means for selecting the waveformparameters comprises: means for identifying a set of codewords foradditional UEs within a threshold distance; and means for varying thewaveform parameters for the at least one chirp with uniform distributionwithin a range such that a distance is maximized between the selectedcodeword and the identified set of codewords.
 19. The apparatus of claim16, wherein the means for transmitting the indication of the one or moreof the selected waveform parameters comprises: means for broadcastingthe indication of the one or more of the selected waveform parameters onone or more side-communication channels between the UE and one or moreadditional UEs.
 20. The apparatus of claim 16, wherein the means fortransmitting the indication of the one or more of the selected waveformparameters comprises: means for transmitting the indication of the oneor more of the selected waveform parameters on an uplink channel betweenthe UE and a network entity.
 21. The apparatus of claim 16, furthercomprising: means for receiving, from a network entity, information of aset of codewords being used in proximity to the UE.
 22. The apparatus ofclaim 16, further comprising: means for broadcasting a beacon, a codeddiscovery message, or a combination thereof on one or moreside-communication channels between the UE and one or more additionalUEs to indicate a location of the UE.
 23. The apparatus of claim 16,further comprising: means for receiving information of a set ofcodewords used by additional UEs on one or more side-communicationchannels between the UE and one or more of the additional UEs, whereinthe waveform parameters are varied based at least in part on theinformation of the set of codewords used by the additional UEs.
 24. Theapparatus of claim 23, further comprising: means for receiving a set ofbeacons, a set of coded discovery messages, or a combination thereof forthe additional UEs on the one or more side-communication channelsbetween the UE and the one or more of the additional UEs to indicatelocations of the additional UEs; and means for determining a set ofproximity values for the additional UEs with respect to the UE, whereinthe waveform parameters are varied based at least in part on the set ofproximity values for the additional UEs.
 25. The apparatus of claim 16,further comprising: means for identifying, for the radar waveform, arange of interest for interference sources; and means for setting afirst frequency offset for the radar waveform such that an interferencepeak of at least one interference source appears beyond the range ofinterest.
 26. The apparatus of claim 16, further comprising: means forphase-coding one or more chirps of the radar waveform to avoid coherentaddition of chirps with other radar waveforms in the communicationsystem.
 27. An apparatus for suppressing interference implemented by auser equipment (UE) with a radar in a communication system, comprising:a processor; memory coupled to the processor; and instructions stored inthe memory and executable by the processor to cause the apparatus to:select waveform parameters for transmission of a radar waveform, thewaveform parameters being a slope, a frequency offset, a chirp duration,or a combination thereof of a chirp of the radar waveform, wherein theradar waveform comprises a plurality of chirps and the selectingcomprises varying the waveform parameters for at least one chirp of theplurality of chirps; transmit an indication of one or more of theselected waveform parameters over the communication system; and transmitthe radar waveform according to the selected waveform parameters. 28.The apparatus of claim 27, wherein the instructions executable by theprocessor to cause the apparatus to select the waveform parameters arefurther executable to cause the apparatus to select a codeword from acodebook comprising a plurality of codewords, wherein the codewordindicates the selected waveform parameters.
 29. The apparatus of claim28, wherein the instructions executable by the processor to cause theapparatus to select the waveform parameters are further executable tocause the apparatus to: identify a set of codewords for additional UEswithin a threshold distance; and vary the waveform parameters for the atleast one chirp with uniform distribution within a range such that adistance is maximized between the selected codeword and the identifiedset of codewords.
 30. The apparatus of claim 27, wherein theinstructions executable by the processor to cause the apparatus totransmit the indication of the one or more of the selected waveformparameters are further executable to cause the apparatus to broadcastthe indication of the one or more of the selected waveform parameters onone or more side-communication channels between the UE and one or moreadditional UEs.
 31. The apparatus of claim 27, wherein the instructionsexecutable by the processor to cause the apparatus to transmit theindication of the one or more of the selected waveform parameters arefurther executable to cause the apparatus to transmit the indication ofthe one or more of the selected waveform parameters on an uplink channelbetween the UE and a network entity.
 32. The apparatus of claim 27,wherein the instructions are further executable by the processor tocause the apparatus to receive, from a network entity, information of aset of codewords being used in proximity to the UE.
 33. The apparatus ofclaim 27, wherein the instructions are further executable by theprocessor to cause the apparatus to broadcast a beacon, a codeddiscovery message, or a combination thereof on one or moreside-communication channels between the UE and one or more additionalUEs to indicate a location of the UE.
 34. The apparatus of claim 27,wherein the instructions are further executable by the processor tocause the apparatus to receive information of a set of codewords used byadditional UEs on one or more side-communication channels between the UEand one or more of the additional UEs, wherein the waveform parametersare varied based at least in part on the information of the set ofcodewords used by the additional UEs.
 35. The apparatus of claim 34,wherein the instructions are further executable by the processor tocause the apparatus to: receive a set of beacons, a set of codeddiscovery messages, or a combination thereof for the additional UEs onthe one or more side-communication channels between the UE and the oneor more of the additional UEs to indicate locations of the additionalUEs; and determine a set of proximity values for the additional UEs withrespect to the UE, wherein the waveform parameters are varied based atleast in part on the set of proximity values for the additional UEs. 36.The apparatus of claim 27, wherein the instructions are furtherexecutable by the processor to cause the apparatus to: identify, for theradar waveform, a range of interest for interference sources; and set afirst frequency offset for the radar waveform such that an interferencepeak of at least one interference source appears beyond the range ofinterest.
 37. The apparatus of claim 27, wherein the instructions arefurther executable by the processor to cause the apparatus to phase-codeone or more chirps of the radar waveform to avoid coherent addition ofchirps with other radar waveforms in the communication system.
 38. Anon-transitory processor-readable storage medium having stored thereonprocessor-executable instructions configured to cause a processor of anapparatus to suppress interference implemented by a user equipment (UE)with a radar in a communication system, the processor-executableinstructions configured to cause the processor to: select waveformparameters for transmission of a radar waveform, the waveform parametersbeing a slope, a frequency offset, a chirp duration, or a combinationthereof of a chirp of the radar waveform, wherein the radar waveformcomprises a plurality of chirps and the selecting comprises varying thewaveform parameters for at least one chirp of the plurality of chirps;transmit an indication of one or more of the selected waveformparameters over the communication system; and transmit the radarwaveform according to the selected waveform parameters.
 39. Thenon-transitory processor-readable storage medium of claim 38, whereinthe processor-executable instructions configured to cause the processorto select the waveform parameters are further configured to cause theprocessor to select a codeword from a codebook comprising a plurality ofcodewords, wherein the codeword indicates the selected waveformparameters.
 40. The non-transitory processor-readable storage medium ofclaim 39, wherein the processor-executable instructions configured tocause the processor to select the waveform parameters are furtherconfigured to cause the processor to: identify a set of codewords foradditional UEs within a threshold distance; and vary the waveformparameters for the at least one chirp with uniform distribution within arange such that a distance is maximized between the selected codewordand the identified set of codewords.
 41. The non-transitoryprocessor-readable storage medium of claim 38, wherein theprocessor-executable instructions configured to cause the processor totransmit the indication of the one or more of the selected waveformparameters are further configured to cause the processor to broadcastthe indication of the one or more of the selected waveform parameters onone or more side-communication channels between the UE and one or moreadditional UEs.
 42. The non-transitory processor-readable storage mediumof claim 38, wherein the processor-executable instructions configured tocause the processor to transmit the indication of the one or more of theselected waveform parameters are further configured to cause theprocessor to transmit the indication of the one or more of the selectedwaveform parameters on an uplink channel between the UE and a networkentity.
 43. The non-transitory processor-readable storage medium ofclaim 38, wherein the processor-executable instructions are furtherconfigured to cause the processor to receive, from a network entity,information of a set of codewords being used in proximity to the UE. 44.The non-transitory processor-readable storage medium of claim 38,wherein the processor-executable instructions are further configured tocause the processor to broadcast a beacon, a coded discovery message, ora combination thereof on one or more side-communication channels betweenthe UE and one or more additional UEs to indicate a location of the UE.45. The non-transitory processor-readable storage medium of claim 38,wherein the processor-executable instructions are further configured tocause the processor to receive information of a set of codewords used byadditional UEs on one or more side-communication channels between the UEand one or more of the additional UEs, wherein the waveform parametersare varied based at least in part on the information of the set ofcodewords used by the additional UEs.
 46. The non-transitoryprocessor-readable storage medium of claim 45, wherein theprocessor-executable instructions are further configured to cause theprocessor to: receive a set of beacons, a set of coded discoverymessages, or a combination thereof for the additional UEs on the one ormore side-communication channels between the UE and the one or more ofthe additional UEs to indicate locations of the additional UEs; anddetermine a set of proximity values for the additional UEs with respectto the UE, wherein the waveform parameters are varied based at least inpart on the set of proximity values for the additional UEs.
 47. Thenon-transitory processor-readable storage medium of claim 38, whereinthe processor-executable instructions are further configured to causethe processor to: identify, for the radar waveform, a range of interestfor interference sources; and set a first frequency offset for the radarwaveform such that an interference peak of at least one interferencesource appears beyond the range of interest.
 48. The non-transitoryprocessor-readable storage medium of claim 38, wherein theprocessor-executable instructions are further configured to cause theprocessor to phase-code one or more chirps of the radar waveform toavoid coherent addition of chirps with other radar waveforms in thecommunication system.